Coadsorption phase diagram for Kr/CCl₄ on graphite

We present the results of an extensive calorimetric study of krypton coadsorbed on graphite precoated with a saturated monolayer of carbon tetrachloride. Combining the heat capacity data with film equation of state measurements from a previous study [W. J. Weber and D. L. Goodstein, Phys. Rev. Lett. 83, 3888 (1999)] permits construction of the Kr/CCl₄ coadsorption phase diagram between 77 and 130 K. Kr succeeds in displacing the CCl₄ from the surface, by a continuous process which results, at lower temperatures, in a film indistinguishable from that of pure Kr adsorbed on graphite. At higher temperatures, a new first-order phase transition, unique to the coadsorption system, is observed and likely indicates a transition to a mixed Kr/CCl₄ film. Finally, measurements at higher Kr coverages reveal evidence for a high temperature extension of the reentrant layering phenomena previously observed for Kr on graphite.